This invention relates to a dispensing system for liquids, especially polyurethane foam precurser chemicals, and more particularly involves the use of an elastic membrane or bladder as one element of the propulsion means. I find that such construction provides a trouble-free long term pump which is useful over many pumping cycles.
The art of pumping liquids goes back a long way and literally thousands of different types of such devices undoubtedly exist. Classically, these have taken the form of mechanical devices of varying degrees of complexity and sophistication. In later historical times, some type of piston is usually found. And the materials of construction have often times varied as a function of the characteristics of the liquid, e.g., corrosive v. non-corrosive, that the pump is intended to be used with.
My principal aim in the present invention is to provide a rather simple pump with ease of operation, ready servicing when necessary, and which is so relatively inexpensive that its replacement imposes no substantial economic harm. Friction is hardly a factor and except for a pair of fluid in and fluid out ball valves and the bladder, there are no other moving mechanical parts in the pump. The pump operates merely by means of compressed gas, especially air, and no other energy sources are required. The air drives a tubular elastic member, the expansion of which propels the fluid out and the contraction of which serves to draw fluid into the pump body for the next pumping cycle. Such pump is, therefore, cyclical in operation.
The heart of the present pump and the present dispensing system is a tubular elastic member which is impervious to both the gas which causes it to expand and the liquid or fluid which it drives. The elastic member or bladder is fitted around a tubular support form and clamped at the ends thereof. Such assembly is positioned within a casing and when the bladder is expanded liquid is pumped out in a path that includes both the extra tubular and intratubular volumes. With the use of the tubular support liquid can always be expelled from my system regardless of the manner in which the expanded bladder fills the volume between casing and tube.
There are certain prior art patents which involve the use of elastic members to propel liquids from a container but none of such patents disclose the construction of the present pumping member.
U.S. Pat. No. 3,225,967 discloses a pumping system wherein the material to be propelled is contained within a bag-shaped diaphragm of rubber-elastic material and a surrounding gas within the container pressing against the bag provides the propulsion force. When the bag has beem emptied the unit is either thrown away or conceivably it can be refilled and reused but it nowhere has the continuous recycling utility of my invention. The system therein described is comparable to the common pressurized cans except that therein the inventor was addressing the problem of expelling contents which are somehow immiscible with the propelling gas. U.S. Pat. No. 3,240,399 is comparable in its mode of operation.
U.S. Pat. No. 3,361,303 discloses a liquid dispenser wherein the liquid is container within a stressed flexible bag and the propulsion force comes from the bag pressing upon the liquid. U.S. Pat. Nos. 3,672,543, 3,876,115 and 3,940,026 operate on substantially the same principles.
U.S. Pat. No. 2,109,549 discloses a means of evacuating a wedge shaped package by air pressure deforming an elastic member surrounding the package. The basic purpose appears to be the complete evacuation of containers of viscous liquids, e.g., grease.
U.S. Pat. No. 3,067,810 is directed to a fuel tank construction wherein air pressure is used to collapse a bladder unit which contains the fuel or other liquid.
None of the foregoing disclose the use of a tubular bladder member as described herein.
Accordingly a principal object of my invention is to provide a novel fluid pumping means employing a tubular, elastic bladder member.
Another object of my invention is to provide a novel liquid dispensing system utilizing said pumping means.
A more specific object of my invention is to provide a system for dispensing reactive liquids such as polyurethane chemicals and the like.